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Xiao, Yang
Universite Paris-Saclay, Ecole Doctorale no. 576: Particules, hadrons, energie et noyau - instrumentation, imagerie, cosmos et simulation - Pheniics, Gif-sur-Yvette (France); Faculte des sciences d'Orsay, Laboratoire de Physique des 2 Infinis Irene Joliot-Curie - IJCLab, Orsay (France); Universite Beihang, Beijing (China)2022
Universite Paris-Saclay, Ecole Doctorale no. 576: Particules, hadrons, energie et noyau - instrumentation, imagerie, cosmos et simulation - Pheniics, Gif-sur-Yvette (France); Faculte des sciences d'Orsay, Laboratoire de Physique des 2 Infinis Irene Joliot-Curie - IJCLab, Orsay (France); Universite Beihang, Beijing (China)2022
AbstractAbstract
[en] Studying nuclear structure and nuclear reactions based on the microscopic nuclear forces has been a central topic in nuclear physics since its inception. However, tricky puzzles rooted in conventional microscopic nuclear forces - for example, the neutron-deuteron scattering analyzing power Ay which has not been described consistently even with the inclusion of three-nucleon forces - demand further studies of the nuclear force in a model-independent approach. In recent years, countless studies of nuclear structure, reactions, and astrophysics in a covariant framework - such as covariant density functional theory, the Dirac-Bruckner-Hartree-Fock method, and Dirac phenomenology - have achieved great success, highlighting the importance of Lorentz invariance in nuclear systems. However, due to lack of high-precision covariant chiral nuclear forces, the CD-Bonn potential is widely used in present nuclear relativistic many-body methods, which can be regarded as a compromise. This motivates the study of the nuclear force in covariant chiral effective field theory to provide further insights to the aforementioned schemes, and to explore whether the covariant chiral nuclear force can overcome longstanding problems. In addition, most of the present chiral nuclear forces contain only the ground-state nucleon, with the contributions from baryon excited states relegated to higher-order low-energy constants (LECs). The explicit inclusion of the Δ(1232) has been proven to improve the convergence of the chiral nuclear force. However, compared with the comprehensive studies of the Δ-full chiral nuclear force, the role of Roper resonance (N(1440)) is still unknown. Since the Roper mass is only about 200 MeV larger than the Δ(1232)'s, its contribution to the nuclear force also needs to be studied. In this thesis, we derive the critical input to the construction of high-precision covariant chiral nuclear forces and quantify the contributions to the chiral nuclear force from the Roper resonance: We adopt a covariant version of naive dimensional analysis and construct the two-nucleon contact Lagrangian constrained by Lorentz, parity, charge conjugation, and hermitian conjugation symmetries. Employing the covariant baryon chiral perturbation theory, we calculate the leading- and next-to-leading-order two-pion exchange (TPE) contributions to nucleon-nucleon (NN) interaction up to order O(q3). The relativistic corrections play an important role in F waves, especially the 3F2 partial wave. We derive the long-range components of the NN TPE potential with an intermediate Roper resonance. Leading-order interactions in heavy baryon chiral perturbation theory are considered. We show that the Roper contribution is sizeable for D waves and improves slightly the description of phase shifts for all the partial waves. The work presented in this thesis is an essential building block for the construction of high-precision covariant chiral nuclear forces, as well as the chiral nuclear force with explicit baryon resonances. (author)
[fr]
L'etude de la structure et des reactions nucleaires sur la base d'interactions nucleaires microscopiques est un sujet central de la physique nucleaire depuis ses debuts. Cependant, des problemes delicats ancres dans les interactions nucleaires microscopiques conventionnelles - par exemple, l de diffusion neutron-deuteron Ay qui n'a pas ete decrit de maniere coherente meme avec l'inclusion des forces a trois nucleons - exigent des etudes supplementaires de l'interaction nucleaire dans une approche modele-independant. Ces dernieres annees, de nombreuses etudes concernant la structure, les reactions et l'astrophysique nucleaires dans un cadre covariant - telles que la theorie de la fonctionnelle de la densite covariante, la methode de Dirac-Bruckner-Hartree-Fock et la phenomenologie de Dirac - ont connu un grand succes, soulignant l'importance de l'invariance de Lorentz dans les systemes nucleaires. Cependant, en raison de l'absence de forces nucleaires chirales covariantes de haute precision, le potentiel CD-Bonn est largement utilise dans les methodes relativistes actuels du traitement du probleme a Ncorps, ce qui peut etre considere comme un compromis satisfaisant. Cela motive l'etude de l'interaction nucleaire dans le cadre de la theorie des champs effectifs chiraux covariants afin de fournir des informations supplementaires sur les schemas mentionnes precedemment et d'explorer si l'interaction nucleaire chirale covariante peut surmonter des problemes de longue date. En outre, la plupart des interactions nucleaires chirales actuelles ne prennent en compte que l'etat fondamental des nucleons, les contributions des etats excites baryoniques etant releguees aux constantes de basse energie (LEC) d'ordre superieur. Il a ete prouve que l'inclusion explicite du Δ(1232) ameliore la convergence de l'interaction nucleaire chirale. Cependant, par rapport aux etudes exhaustives de l'interaction nucleaire chirale Δ, le role de la resonance de Roper (N(1440)) est encore inconnu. Puisque la masse de Roper n'est que d'environ 200 MeV plus importante que celle de Δ(1232), sa contribution a l'interaction nucleaire doit egalement etre etudiee. Dans cette these, nous derivons les parametres d'entrees critiques pour la construction des interactions nucleaires chirales covariantes de haute precision et quantifions les contributions de la resonance de Roper a la force nucleaire chirale: On adopte ici une version covariante de l'analyse dimensionnelle naive et construisons un lagrangien de contact a deux nucleons contraint par les symetries de Lorentz, la parite, la conjugaison de charges et la conjugaison hermitienne. A l'aide de la theorie des perturbations chirale baryonique covariante, nous calculons les contributions d'echange a deux pions (TPE) au premier ordre et a l'ordre suivant a l'interaction nucleonnucleon (NN) jusqu'a l'ordre O(q3). Les corrections relativistes jouent un role important dans les ondes F, en particulier l'onde partielle 3F2. Nous derivons les composantes a longue portee du potentiel TPE NN avec une resonance intermediaire de Roper. Nous montrons que la contribution de Roper est importante pour les ondes D et ameliore legerement la description des dephasages pour toutes les ondes partielles. Le travail presente dans cette these represente un element essentiel pour la construction d'interactions nucleaires chirales covariantes de haute precision, ainsi que d'interaction nucleaire chirale avec des resonances baryoniques explicites. (auteur)Original Title
Diffusion nucleon-nucleon dans la theorie des champs effective chirale covariante
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Source
3 Jun 2022; 92 p; 140 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; These de doctorat de l'universite Paris-Saclay, Specialite: Structure et reactions nucleaires
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Miscellaneous
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Thesis/Dissertation
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BARYON-BARYON INTERACTIONS, BARYONS, BOSON-EXCHANGE MODELS, ELEMENTARY PARTICLES, FERMIONS, FIELD THEORIES, FUNCTIONS, HADRON-HADRON INTERACTIONS, HADRONS, INTERACTIONS, MATHEMATICAL MODELS, N BARYONS, N*BARYONS, OBE MODEL, PARTICLE INTERACTIONS, PARTICLE MODELS, PARTICLE PROPERTIES, PERIPHERAL MODELS, SYMMETRY
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